This is a Phase II SBIR proposal to develop a new therapy for the treatment of asthma. The desired outcome will be the identification of a therapeutic candidate to replace theophylline, a non-selective adenosine receptor antagonist that is effective in treating asthma, but limited by side effects, primarily insomnia, mediated by blockade the A1AR in the brain. This proposal continues the collaboration between a biotechnology company, Adenosine Therapeutics, LLC (ATL) located in Charlottesville, VA and the University of Virginia laboratory of Joel Linden, PhD, an expert in the study of adenosine receptors. The now completed Phase I SBIR proposal was predicated on the hypothesis that antagonists of the A2B adenosine receptor (A2BAR) inhibit allergen-mediated activation of mast cells. This was based on the observation that selective A2B blockers such as our proprietary compound, MRS1754, inhibit adenosine-mediated activation of certain mast cell lines such as canine BR and human HMC-1 mast-like cells. In Phase I we optimized procedures for preparing purified human lung mast cells and we showed that these cells have functional A2BARs that facilitate allergen-mediated degranulation. MRS174 is not a therapeutic candidate since it has very low aqueous solubility and poor bioavailability. Chemists at Adenosine Therapeutics, headed by the Principal Investigator of the proposal, Robert Thompson, Ph.D., have now succeeded in synthesizing a new family of proprietary selective A2BAR blockers that are bioavailable and therapeutic candidates. One of the new compounds (ATL829) has been tested in allergic sheep and shown to reduce by > 50% adenosine mediated bronchospasm. The primary goal of this Phase II SBIR application is to identify an A2BR antagonist therapeutic candidate for the treatment of asthma that is orally available, potent, and efficacious in a sheep asthma model. We propose to develop procedure for the large scale synthesis of clinical candidates (Aim 1), screen A2BAR therapeutic candidates for activity on human mast cells (Aim 2) and evaluate oral activity of the test compounds in sheep (Aim 3). We will evaluate three drug candidates in sheep asthma models to identify an optimal lead therapeutic candidate and one backup compound (Aim 4). Sheep studies will be done on a contractual basis by Dr. William Abraham at Mount Sinai Medical Center in Miami Beach, Florida. These objectives directly relate to the mission of the National Institute of Allergy and Infectious Diseases, which is to conduct and support basic and applied research to better understand, treat, and ultimately prevent infectious, immunologic, and allergic diseases, by targeting drug development for asthma, for which current therapies are not ideal for patient care. The goal of this project is to develop improved drugs for the treatment of Asthma, a disease that affects millions of Americans. Exciting new preliminary data in sheep establishes the effectiveness of a new proprietary class of A2B adenosine receptor antagonists. Current therapies are plagued by limited efficacy, tachyphylaxis, or adverse side effects. [unreadable] [unreadable] [unreadable]